Precast hollow core slab cracks

[Keem1408]

One year ago I bought a 2-story house that is built from precast concrete elements (walls and hollow core slabs) with a raft foundation on compacted soil.

I noticed the following;
1- After six months I found (2-3mm) width cracks on the first floor hollow core slab that can be seen from ground floor (See attached photos). Is this a structural cracks I should worry about? And how it is repaired? Note that above that area there’s a bedroom. Hollow core thickness is 25cm.

2- The horizontal joints between the internal walls started to be appear in some areas(See attached photo). Can I cover them by applying a filler mesh then repaint again?

3- There’s a crack in some exterior walls joints sealant (see attached photo). What best thing to do for them?

4- What is kind of sealant typically used for interior and exterior wall to wall joints, and wall to hollow core slab?

Appreciate your advice.

 

[Keem1408]

I’m new here and couldn’t upload more than photo in the post.

Attached is the hollow core slab crack.

 

[Keem1408]

Another photo for slab crack

 

[Keem1408]

This is the horizontal joint between walls

 

[hokie66]

Not sure what type is normally used, but it should be a low modulus sealant which will stretch rather than tear out the concrete. Sikaflex 11FC would be my choice, widely available and ideal for the purpose. Paintable polyurethane. Use with backing rod.

 

[Keem1408]

Thank you hokie. Is it same as Sikaflex Precast?

 

[hokie66]

Probably similar, but I have no experience with that sealant. Suggest you contact Sika.

 

[Keem1408]

Will do. Thank you